Cut-Off Wheel Comprising a Double Core Clamping Device

ABSTRACT

The invention relates to a composite system for a cut-off wheel ( 1 ), in particular with a diameter greater than 400 mm, consisting of an abrasive external cutting ring with depressions ( 3 ) on both sides in the vicinity of the bore, two flush-fitting tensioning plates ( 2 ) being placed in said depressions to act as a core clamping device. Said clamping plates are reusable elements, retained by the user, and transfer forces to the clamping flanges ( 4   a   +4   b ) of the machine. The plates also increase stability and reduce waste.

The instant invention relates to the composite system for a synthetic resin-bonded cut-off wheel with an outer diameter of >=400 mm, with recesses being pressed in the bore region on both sides, two adapted edge-shaped clamping plates being inserted into said recesses as reusable core clamping devices in response to the clamping.

Synthetic resin-bonded cut-off wheels starting at a diameter of >=400 mm are used on stationary separating facilities in the metal-generating as well as metal-processing industry for cutting steel, cast iron, special alloys, inconell, titanium, etc.

The generally slight usability of the conventional cutting wheels thereby proves to be a great disadvantage. In an ideal case, these homogenous cut-off wheels can be used up to a minimum of 45% of the new diameter, but on average they can be used up to only 60% of the initial diameter, in dependence on available machines as well as large material measurements.

These remaining residual discs must then be disposed of at high costs according to the national disposal guidelines. A further disadvantage to be mentioned is the additional use of raw material for these unused core zones, which results in additional costs for the raw material sector in spite of alternative abrasive grain materials in view of reinforcement and resin portion.

European Patent 0382720A2 describes a synthetic resin-bonded fabric-reinforced cut-off wheel by means of a non-positive bonding on a metallic base body. This system, however, was not able to establish itself, because a small residual film of the grind-active edge zone remains on the remaining base body and the need to dispose of a metal core comprising a synthetic resin-bonded residual film still remains.

A further solution is described in EP 0 769 352 A1, wherein, on a metallic base body, the grind-active edge zone is pressed in a non-positive manner directly during the production. Here, the high-priced acquisition of a large number of these base bodies has turned out to be a disadvantage. In addition, there is a logistical problem with reference to the return of the used composite cutting wheel, which must be sent back to the manufacturer so as to be re-plated. For cost reasons, this system can thus only be used at a limited distance to the manufacturer. In addition, the cleaning and re-plating is associated with a greater technical effort and, finally, is a time as well as a cost factor.

DESCRIPTION

It is thus the object of the instant invention to create a composite system, which eliminates the above-mentioned disadvantages and which makes it possible for the user to deplete the external cut-off wheel of up to 95% of the entire grind-active cutting ring surface and which ensures additional advantages, such as a reduced cutting wheel width with even higher stability.

According to the invention, this is achieved in that the bore diameter of the cut-off wheel is synchronized to the minimum depletion diameter and that, additionally, depressions for the edge form of the two clamping plates, being offset on both sides, are pressed in. This enables a virtually complete depletion of the grind-active edge zone and only a small abrasive residual ring must be disposed of.

The two clamping plates, which are to be considered to be connecting elements between the actual clamping flanges at the machine side and the grind-active cutting ring, are essential components of this invention. Due to the fact that specifically the transition from the clamping flange to the cutting wheel for conventional products represents a weak spot, this disadvantage is considerably improved here according to the invention by means of the material of the clamping plates, which is possible as an alternative.

Due to the fact that the two clamping plates remain with the user, only the considerably lighter cutting ring must be sent to the customer and an economy of weight of up to 40% is possible thereby.

Additional features and details of the instant invention can be found from the below description of the figures. It is shown therein:

FIG. 1 an exploded illustration of a cut-off wheel according to the invention with double clamping plates,

FIG. 2 a section through the composite system along the line A-A in FIG. 3 and

FIG. 3 a side view of this cutting ring composite system

The cut-off wheel 1 illustrated in the figures is a synthetic resin-bonded cut-off wheel without, preferably with additional material reinforcement. A systematic selection of phenolic resin in combination with coordinated abrasive grains and fillers, the different degrees of hardness are adapted to the respective application requirements and customer requests.

Corundum, but specifically special corundum, zircon corundum and sinter corundum as well as silicon carbide are used as grinding means. The fillers consist of raw materials, such as pyrite, zinc sulphide, graphite, potassium chlorine manganate etc., which are presently also used in cutting wheels for industrial applications.

Glass material inserts are presently used as material reinforcement 5. In the future, however, alternatives such as Kevlar® or carbon fiber are possible. An embodiment without a continuous reinforcement is possible. However, reinforcements should be provided in the region of the depressions.

The outer diameter D of the cut-off wheel 1 typically lies between 400 and 2000 mm, preferably, however, it is greater than 800 mm. Ideally, the bore diameter d of the cut-off wheel (1) can be adjusted to the applied minimum diameter. For manufacturing reasons, however, a fix bore d should be chosen based on the respective standard measurement of the cutting ring. The range 40-80% of the outer diameter D is to be indicated as the recommended value for the bore diameter d.

Presently, the ratio of the diameter D to the width T typically lies in the range 80-100. According to the invention, due to the considerably stiffer core zone, an increase of up to 130 can be realized. The grind-active cutting ring can be embodied in a plane-parallel as well as in a conical manner, that is, so as to taper towards the bore.

For clarity reasons, the width T in FIGS. 1 and 2 is illustrated many times too large in relation to the diameter D.

On the flat surface in the bore region on both sides, the cut-off wheel 1 encompasses a plurality of geometric depressions 3, into which the two clamping plates are inserted with an exact fit. The shape of this recess 3 can be embodied so as to be round, rectangular, but preferably like a dovetail. To enable a good pretensioning of the clamping plates 2, the depth of these recesses must be between 0.1 and 1 mm, preferably 0.2 to 0.6 mm less than half of the cutting ring width T in the bore. The radial reach e of these recesses 3 is a function of the outer diameter D and is between 10 and 200 mm, preferably between 30 and 60 mm.

The two clamping plates 2, which, with their defined edge shape, fit exactly into the bilateral recesses 3 of the cut-off wheel 1 are a considerable component of this system. In response to the clamping with the conventional clamping flanges 4 a and 4 b, the two clamping plates are compressed and the required lateral clamping force is thus generated. The drive shaft thereby transfers the forces required for a clamping process via the clamping flanges to the two clamping plates and from there they are finally transmitted via the special edge shape to the grind-active, abrasive cutting ring in a non-positive manner.

The clamping plates can be embodied in a straight, offset, perforated or also in a corrugated shape. As a possibility for reducing the weight, the clamping plates can be provided with additional recesses.

The edge shape 3 of these two clamping plates 2 is characterized by a plurality of symmetrically, round, square, dovetail-shaped or similarly formed protruding clamping surfaces, which must fit exactly into the bilaterally pressed depressions of the grind-active cutting ring and which can thus transfer the forces which occur during the abrasive cutting.

The total thickness of the two clamping plates must be slight, i.e. approximately 5-10% thinner than the wheel thickness T in the bore region of the cut-off wheel. In doing so, it is ensured that the required free cutting depth is achieved as with conventional cutting wheels.

High-strength reinforced synthetic materials, carbon fibers, non-ferrous metals, special alloys, titanium, but preferably presently simple steel plates are used as material for these clamping plates. In addition to the required basic strength, it is an important criterion for this material to encompass a certain flexibility and high residual stress, so as to be able to withstand the lateral force effects occurring in response to such applications, without permanent damage.

To facilitate the handling in response to the clamping of this composite system, provision is made in the clamping plates for slits 2 a, into which special tension springs are inserted as a clamping aid. With very large clamping plates (>60% of the outer diameter of the cutting ring), additional bores 2 b can be installed in the outer diameter region of the clamping plates as an additional fixing or clamping force increase. Connecting elements are thereby not to protrude beyond the end face of the clamping plate.

A position and form-exact pressing of the recesses in the bore region of the cut-off wheel is required. This is achieved by pressing a template having an exact fit. In the alternative, these recesses can also be subsequently ground subsequently on a suitable processing facility. 

1. A system for a cut-off wheel (1) having a diameter (D)≧400 mm comprising a mixture of abrasive grit, binders, fillers, if applicable, said system being clamped between two clamping plates (2), with a bore of a grind-active cutting ring (1) only reaching to the outer edge of the two clamping plates and a connection clamping plate (2)—cutting ring (1) occurring only by means of a clamping force and fit of the two clamping plates.
 2. The system for a cut-off wheel (1) according to claim 1, wherein depressions having an exact fit are pressed or subsequently ground on both sides in the bore region.
 3. The system for a cut-off wheel (1) according to claim 1, wherein the grind-active cutting ring (1) is embodied so as to taper towards the bore (d) up to 3 mm in a plane-parallel, preferably conical shape.
 4. The system for a cut-off wheel (1) according to claim 1, wherein the ratio of the diameter (D) of the cut-off wheel (1) to the width (T) lies above 70, preferably above
 90. 5. The system for a cut-off wheel (1) according to claim 1, wherein the bore (d) is greater than 40% of the outer diameter (D).
 6. The system for a cut-off wheel (1) according to claim 1, wherein the grind-active cutting ring (1) is embodied in a synthetic resin-bonded embodiment.
 7. The system for a cut-off wheel (1) according to claim 1, wherein the cut-off wheel (1) encompasses at least one, preferably two or more material inserts (5).
 8. The system for a cut-off wheel (1) according to claim 1, wherein the clamping plates (2) are embodied in an offset, perforated or, preferably, in a straight form, respectively.
 9. The system for a cut-off wheel (1) according to claim 1, wherein the clamping plates (2) are embodied of materials such as carbon fibers, high-strength reinforced synthetic materials, non-ferrous metals, special alloys, titanium, but preferably of a sheet metal.
 10. The system for a cut-off wheel (1) according to claim 1, wherein the edge shape of the clamping plates (2) is adapted to the depressions (3) of the cutting ring (1).
 11. The system for a cut-off wheel (1) according to claim 1, wherein the total width (b) of the two clamping plates (2) is 1 to 20%, preferably 5 to 10% thinner than the width of the cutting ring (1) in the bore (d).
 12. The system for a cut-off wheel (1) according to claim 1, wherein an insulation film is inserted or glued between the clamping plates (2).
 13. The system for a cut-off wheel (1) according to claim 1, wherein slits (2 a) and/or additional bores (2 b) are installed in the clamping plates as a clamping aid or as an additional clamping force reinforcement.
 14. A method for producing a system for a cut-off wheel (1) according to claim 1, wherein the lateral depressions (3) are already pressed or, in the alternative, subsequently ground by means of templates, whereafter two clamping plates (2) are fitted into the depressions (3). 